Apparatus for evacuating drilling fluids from a well

ABSTRACT

Disclosed is an apparatus and related method for evacuating drilling fluids from between axially spaced well packers in which a circulating joint is disposed between the packers in a tubing string that penetrates both packers. Pressure is applied to the tubing string to unblock circulating ports through the joint, allowing circulation into the area between packers and out of the well in a shorter tubing string penetrating only the upper packer. After circulation, pressure is applied to the long string causing the joint ports to be closed. The circulating joint comprises a tubular body with circulating ports through its walls and a sleeve assembly surrounding the body blocking the ports. Expansible chambers between the sleeve and body are employed to first unblock the ports and then to block them again upon selective introduction of pressure to the chambers.

United States Patent [1 1 Cochran May 13, 1975 [541 APPARATUS FOR EVACUATING DRILLING 3,750,752 8/1973 Mott 160/224 R FLUIDS FROM A WELL Primary Examiner-James A. Leppink [75] lnvemor' ggr Cmhran Houston Attorney, Agent, or Firm-Torres & Berryhill [73] Assignee: gzzwn Oil Tools, Inc., Houston, [57] ABSTRACT Disclosed is an apparatus and related method for 1 F1199? 18, 1974 evacuating drilling fluids from between axially spaced 1 4 well packers in which a circulating joint is disposed [211 App No.. 3 ,838

Related U.S. Application Data between the packers in a tubing string that penetrates both packers. Pressure is applied to the tubing string to unblock circulating ports through the joint, allowing circulation into the area between packers and out of the well in a shorter tubing string penetrating only the upper packer. After circulation, pressure is applied to the long string causing the joint ports to be closed. The circulating joint comprises a tubular body with circulating ports through its walls and a sleeve assembly surrounding the body blocking the ports. Expansible chambers between the sleeve and body are employed to first unblock the ports and then to block them again upon selective introduction of pressure to the chambers.

16 Claims, 4 Drawing Figures APPARATUS FOR EVACUATING DRILLING FLUIDS FROM A WELL This is a division of application Ser. No. 186,994, filed Oct. 6, 1971, now US. Pat. No. 3,799,268.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention pertains to drilling and completion of oil and gas wells. More specifically, it concerns circulating apparatus for evacuating drilling fluids from tubing strings and the space between packers in a completion competion well.

2. Description of the Prior Art When completing a multiple zone well, it is necessary to displace drilling fluid (mud) which remains standing in the well after drilling operations. In a dual completion well, this requires circulating fluid down the long string and back up through the short string. It is desirable to perform this operation after the tubing strings are secured at the wellhead, so as to be under full pressure control. In the past, this operation has been performed prior to setting either the permanent (lower) packer or the hydraulic (upper) packer. Thus, the circulating fluid passes out of the longer string back up around the permanent packer and displaces the drilling fluid between packers through the short string and around the hydraulic packer through the surrounding casing. After the drilling fluid has been removed, both the permanent packer and the hydraulic packer are set. One disadvantage of such a method is the possibility of a blowout in the lower and/or upper zone prior to setting the packers. In addition, since the drilling fluid passes around packers prior to setting, the distinct possibility exists that the packer seals will be damaged by the erosive passage of drilling fluid around the packers. Of course, if the packers do not properly seal when they are set, an expensive pulling job may be required.

Attempts have been made to overcome the disadvantage of the former displacement procedure. For example, a circulating -joint has been attached to the long string for disposition between the permanent and hydraulic packers. The joint is provided with ports which may be opened or closed by running a wireline tool into the joint through the long string. But wireline tools are susceptible to becoming stuck in the tubing string. This is particularly true when the string is filled with drilling mud.

Pressure operated apparatus has been recently developed to eliminate wireline tools. Such apparatus also employs a circulatingjoint carried by the long string for disposition between packers and having ports which may be opened by applying pressure to the long string. In this method, the permanent packer may be set prior to circulation and the circulating fluid flows from the long string into the space between packers, displacing the drilling fluid through the short string and around the unset hydraulic packer. After circulation, the circulating sleeve ports are closed by setting the hydraulic packer and the well is ready for production. Although such a procedure reduces blowout hazards of the lower zone and allows running, setting and testing of the permanent packer and long string before the short string is run, it does not eliminate the blowout hazards of the upper zone nor the possibility of damaging the seals of the unset hydraulic packer. Furthermore, the apparatus for performing this procedure is very complex, requiring, among other things, extremely close tolerances to operate properly and precise adjustment of the apparatus for different weight pipes and distance between packers. The closing of the circulating ports is also dependent upon the proper setting of the hydraulic packer. These features result in a rather expensive, delicate and relatively bulky device.

SUMMARY OF THE INVENTION The present invention discloses a circulating joint which eliminates the problems of the former methods of drilling fluid evacuation. The joint is attached to the long string and run into the well for disposition between the lower permanent packer and the upper hydraulic packer. The joint is also provided with ports which are closed until the permanent packer and possibly the hydraulic packer are set. Pressure is then applied to the long string, causing a pressure chamber in the joint to expand and uncover these ports. Circulating fluid, such as water, is then circulated through the long string and the circulating joint ports, into the area between packers, and back up through the short string, displacing drilling fluid from the long string and the area between packers. After the drilling fluid is displaced, a ball member is dropped into the longer string to seat on a portion of the circulating sleeve. Increasing pressure is applied to the ball until the sleeve assembly is displaced from its initial position to again cover and seal the circulating ports. A further increase in pressure causes the ball and its corresponding seat to be displaced from the joint and to be dropped into the bottom of the well, leaving the well ready for production.

Thus, the circulating joint of the present invention allows setting of both the permanent and hydraulic packers prior to displacement of drilling fluids, eliminating hazards of blowout in either zone and eliminating the possibility of damage to either packer from the flow of erosive drilling fluids. Both zones may be under complete pressure protection at all times and the circulating ports in the circulating joint are closed independently of the short string or the setting of the hydraulic packer and without wireline tools. The apparatus is simple and economically manufactured. Other objects and advantages of the invention will become apparent from the description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS In the description of a preferred embodiment of the invention which follows, reference will be made to the accompanying drawings in which:

FIG. 1 is a diagrammatic representation of a dual completion well having long and short strings, a lower permanent packer and an upper hydraulic packer in set positions, and employing a circulating joint shown in the port open position, for circulating fluid through the long string and back up the short string to displace drilling fluids from the long string and between the packers, according to a preferred embodiment of the invention;

FIG. 2 is a quarter-sectional elevation view of the circulating joint of FIG. 1, in its initial closed position;

FIG. 3 is a quarter-sectional elevation view of the circulating joint of FIGS. 1 and 2, in its port opened position; and

FIG. 4 is a quarter-sectional elevation view of the circulating joint of FIGS. 1-3, shown in its final closed posltion.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring first to FIG. 1, there is shown a well for producing petroleum fluids from upper and lower subterranean formations or zones. An outer conduit or casing string extends from the surface 11 to the bottom 16 of the well hole. The casing string 10 is perforated at 12 and 14 to allow flow of petroleum deposits from the lower and upper zones, respectively. A wellhead 15 is attached at the upper end of the casing string 10 and provides support for a pair of tubing strings, long string 21 and short string 22. The long string 21 extends downwardly through the casing string 10 past the upper production zone into an area adjacent the lower production zone. The short string 22 extends from the wellhead to a point in the casing string 10 adjacent the upper production zone.

Normally, the permanent (lower) packer 25 is run into the well, set and tested first. Then the long string 21 is run into the well with a hydraulic (upper) dual packer 26 attached thereto. Next, the short string 22 is run into the well and through the hydraulic packer 26. Both strings are secured at the wellhead 15. The hydraulic packer 26 can be set and tested at this point.

I-Iowever, it might be desirable to leave the packer 26 unset during the period of drilling fluid displacement.

Attached in the long string at some point between the permanent packer 25 and hydraulic packer 26 is a circulating joint, designated generally by the reference number 50. This circulating joint 50 will be described in more detail hereafter. For present purposes it is sufficient to state that the circulating joint 50 is provided with ports which are initially closed during the running of the tubing strings 21, 22. After the permanent packer 25 has been set and both strings run in place, pressure may be applied through the long string 21 causing these ports to be opened, as will be more fully understood hereafter. Circulating fluid, such as water, is then circulated through the long string 21, out the circulating joint ports, into the area of the casing string 10 between permanent packer 25 and hydraulic packer 26, and back up the short string 22 (see the arrows in FIG. 1). Thus, the drilling fluid which has accumulated in long string 21 and the area between packers 25, 26 is displaced from the well. Further pressure is then applied to the circulating joint 50, as will be explained hereafter, causing the circulating joint ports to again be closed. If the hydraulic packer 26 has not already been set, it is set at this time and the well is ready for production.

Referring also now to FIGS.' 2, 3 and 4, the circulating joint 50 will be described in detail. The joint comprises a tubular body member 52 which is provided at each end with means for connection in a tubing string. In the particular embodiment shown, the lower end is provided with male threads 53 and the upper end is provided with male threads 54 for connection to a threaded collar 55. The body 52 is provided with three axially spaced sets of radial ports 56, 57, 58. The lower set of ports 58 are the circulating ports referred to in describing FIG. 1. The intermediate ports 57 and upper ports 56 are pressure ports, necessary for operating the circulating joint as described hereafter.

Initially fastened in the bore of tubular body 52 between ports 56 and 57, by a shear screw 61, is a cylindrical spool piece or seat member 62. The outside diameter of seat member 62 is slightly less than the upper bore 51 of tubular body 52. Annular seals 63, 64 provide sealing engagement between the seat member 62 and upper bore area 51. The mid-portion 65 of seat member 62 may be reduced in diameter. A frustoconical seating surface 68 is provided at the upper end of seat member 62 for reasons to be shown hereafter.

Surrounding the tubular body member 52, in a sliding fit is a sleeve assembly, designated generally by the reference number 70. This sleeve assembly 70 comprises a lower skirt member 80, a seal carrying sleeve 90, a pressure chamber sleeve 100 and a retaining sleeve 110. Initially, the entire sleeve assembly is axially maintained in the position shown in FIG. 2 by a shear connection 119 with tubular body 52. A stop ring 40 assures that upward drag forces do not disrupt the connection 119. Skirt member is attached to seal carrying sleeve by a shear screw 81. The remaining sleeve members 90, and are assembled as an integral unit by threaded connections 91 and 101. Seals 92 and 102 assure that these are fluid-tight connections.

Mounted around tubular body 52 in an axially spaced relationship are a pair of seal assemblies and 130. Each seal assembly 120, 130 is provided with internal 121, 131 and external 122, 132 seal rings. Upper seal assembly 120 is held in place by a pair of retainer rings and 126 while lower seal assembly is held in place by a pair of similar retainer rings 135 and 136.

The pressure chamber sleeve 100 is also provided with a seal ring 104. The seal assemblies 120, 130 and seal ring 104 cooperate with tubular body 52 and the sleeve assembly 70 to form a pair of annular variable volume or expansion chambers 72, 74 between tubular body 52 and sleeve assembly 70. The upper chamber 74 communicates with the upper bore 51 of body 52 through the upper set of ports 56. The lower chamber 72 communicates with the counterbore area 51a of tubular body 52 through the intermediate set of ports 57.

In the initial, or running in, position of the circulating joint shown in FIG. 2, the skirt member 80 blocks passage of fluid from the interior of body 52. Seal rings 94 and 84 cooperate to form a pressure chamber 85 communicating with the counterbore 51a of tubular body 52 through circulating ports 58. After the tubing string, to which the circulating joint is attached, has been landed and circulation is desired, the circulation ports 58 must be opened. This is accomplished by applying pressure to the tubing string, in which the circulating joint 50 is installed. The expansion chambers 74 and 72 are exposed to this pressure through ports 56 and 57, respectively. Since the pressure in these chambers act in opposite directionson the opposed equal annular surface areas 106.and 108 of the sleeve assembly 70, the resulting force tending to break the shear connection 119 is zero, so that the sleeve assembly components 90, 100 and 110 remain in the position shown in FIG. 2.

This same pressure also communicates with the chamber 85, partially formed by skirt member 80. However, in this chamber, the opposing forces on annular areas 96 and 86 apply a shear stress to the shear screw 81. As soon as the pressure in the tubing string reaches a value sufficient to shear this screw 81, say 1,000 to 1,200 psi, the skirt member 80 is axially displaced to the position shown in FIG. 3 where it is stopped by contact with body shoulder 60. If a sufficient pressure cannot be maintained by the lower production zone, a ball member may be dropped through the circulating joint into engagement with a seat member installed atthe lower end of the tubing string, similar to the circulating joint seat member 62. This would close off the end of the tubing string and allow pressure to be increased. After the skirt member 80 has been displaced to the position shown in FIG. 3, the circulating ports 58 are then unblocked and free for passage of drilling fluid and circulating fluid from the long tubing string into the area surrounding the long string between permanent packer 25 and hydraulic packer 26 (FIG. 1 As shown in FIG. 1, the circulating fluid is pumped through the long string 21, out the circulating joint ports and back up through the short string 22, displacing the drilling fluid which has accumulated in the long string and in the area between packers 25 and 26.

After the drilling fluid has been displaced, it is necessary to once again seal off the circulating ports 58 to prevent comingling of production between the two production zones. This is accomplished by first dropping a rubber ball 140 down the long string until it engages the seating surface 68 of seat member 62 as shown in H0. 4. The ball 140 and seat 62 may be considered to be a valve. Now, when pressure is applied to the tubing string, chamber 74 is subjected to the same pressure, but chamber 72 is isolated from that pressure by the closed valve, ball 140 and seat 62, and is at the lower pressure existing in the counterbore area 51a of tubular body 52. When the differential pressure between surfaces 106 and 108 is great enough, the shear connection 119, between sleeve assembly 70 and tubular body 52, fails and allows the remaining portion of sleeve assembly 70 to be axially displaced downwardly to the position shown in FIG. 4. A small port 109 equalizes pressure in the annular space 107 between seal assembly 130 and the upper end of seal carrying sleeve 90. To prevent the entrapment of fluid between the lower end of seal carrying sleeve 90 and skirt member 80, longitudinal slots 59 are provided on the lower exterior of body member 52. This allows passage of fluid by the seal ring 84.

The upper seal assembly 120 is provided with a snap ring 127 which is outwardly biased. As soon as the sleeve assembly 70 is displaced downwardly a proper distance, this snap ring 127 springs into engagement with the shoulder 112 of retainer sleeve 110, preventing upward movement of the sleeve assembly 70 and maintaining it in the port blocking position shown in FIG. 4. As the sleeve assembly 70 is displaced downwardly it carries a pair of annular seal rings 97, 98 to the position shown, one above and one below the ports 58, sealing and blocking further passage through circulating ports 58.

Once the circulating ports 58 have again been closed, it is necessary to remove the ball member 140 and seat member 62. This is accomplished by increasing the pressure in the tubing string until shear screw 61 is sheared, allowing the seat member 62 and ball 140 to drop out the end of the tubing string into the bottom of the well hole. If it had been necessary to place a similar ball in the bottom end of the string in order to accomplish the initial opening of circulating ports 58, the ball 140 and seat member 62 would stop at this point until further pressure is applied to remove that seat member and ball. In such a case, both sets of seat members and balls would be dropped into the bottom of the well hole. If the hydraulic packer 26 (see FIG. 1) had already been set, the well would now be ready for production. If not, the hydraulic packer 26 would be set at this point and the well would be ready for production.

The circulating joint of the present invention offers several alternatives for setting of the hydraulic packer. It could be set prior to circulation by applying pressure through the short string 22. In such packers, it is common to drop a ball through the short string so as to allow pressure to be applied to the packer. This ball could then be pumped back to the surface during the circulating operations. Another way to set the hydraulic packer 26 would be to apply pressure to the packer through the long string when the ball is seated on the seat member 62 as shown in FIG. 4. Still another would be to set the packer after circulation and reclosing of the circulating joint by applying pressure through the short string 22, with a ball and seat device similar to the ones (140, 62) used in the circulating joint 50. After setting of the packer, the ball and seat would be pressured out the bottom of the short string to clear the string for production. Other alternatives for setting the hydraulic packer could be used. These are only examples to illustrate the flexibility of the present invention.

Thus, it can be seen from the foregoing description, that the circulating joint of the present invention offers a much improved method of evacuating drilling fluid from the long string and the area between packers in a multiple completion well. The circulating joint is operated by pressure and without the use of wireline tools. The method is very easy to perform and can be done after setting of both the permanent packer and hydraulic packers to prevent damage to packer seals and to maintain all production zones under full pressure control. The apparatus is simple and its manufacture is economically attractive. Operation of the circulating joint is dependent on pressure alone and does not require manipulation of a tubing string for opening and closing of circulating ports.

Although only one embodiment of the apparatus of the invention has been shown herein, several methods of its use have been described. Further variations of the apparatus and methods disclosed herein will be apparent to those skilled in the art. It is therefore intended that the scope of the invention be limited only by the claims which follow.

I claim:

1. Pressure operated apparatus comprising:

a. tubular body means having port means through the walls thereof;

b. sleeve means surrounding said body means in a first position blocking fluid flow through said port means, said sleeve means including a skirt member axially movable on the existence of a predetermined pressure level in said body means to unblock flow through said port means; and

c. expansible chamber means between said body means and said sleeve means, pressure operable after said unblocking of said port means to axially reposition said sleeve in a second position blocking flow through said port means;

d. said skirt member having an annular surface thereon which in said first position forms a portion of a pressure chamber communicating with the interior of said body means through said port means, said skirt member being fastened to the rest of said sleeve means in said first position by connection means, said connection means being releasable on exposure of said annular surface to said predetermined pressure level to permit said axial movement of said skirt means to unblock said as?! means.

2. Pressure operated apparatus as set forth in claim 1 in which said expansible chamber means comprises first and second annular chambers communicating with the interior of said body means through first and second ports, respectively.

3. Pressure operated apparatus as set forth in claim 2 in which said first chamber is partially defined by said annular surface on said skirt member, said second chamber being partially defined by an oppositely facing annular surface on said sleeve means.

4. Pressure operated apparatus as set forth in claim 3 in which valve means is installed in said body means between said first and second ports, said valve means being closable to pressure isolate one end of said body means interior and said first chamber from the other end of said body means interior and said second chamber.

Pressure operated apparatus as set forth in claim 4, in which said valve means comprises a seat member affixed to said body means in sealing engagement with its interior and a closure member sealingly engageable with said seat member.

6. Pressure operated apparatus as set forth in claim 5 in which said seat member is affixed to said body means by connection means which is releasable, when said valve means is closed, at a predetermined pressure differential between said first and second chambers.

7. A pressure operated circulating joint for installation in a pipe string, comprising:

a. tubular body means having connection means at each end thereof for connection with adjacent sections of said pipe string;

b. circulating port means through the walls of said body means;

c. tubular blocking means surrounding said body means in a position blocking flow of fluid through said circulating port means and axially movable to a position unblocking flow through said circulating port means;

d. sleeve means surrounding said body means and axially movable when said blocking means is in said unblocking position, from a first position to a second position, blocking flow through said circulating port means;

e. chamber means between said body means and said blocking means and said sleeve means, exposable to pressure in said body means, to effect said axial movements of said blocking means and said sleeve means; and

f. releasable means connecting said blocking means to said sleeve means allowing separation of said blocking means from said sleeve means on the introduction of a predetermined pressure level into said chamber means.

8. A pressure operated circulating joint as set forth in claim 7 in which said chamber means comprises an annular chamber at least partially defined by the interior of said blocking means and in fluid communication with the interior of said body means through said circulating port means.

9. A pressure operated circulating joint as set forth in claim 7 in which said sleeve means is connected to said body means by second releasable means allowing said axial movement thereof on the existence of a predetermined pressure differential in said chamber means.

10. A pressure operated circulating joint as set forth in claim 9 in which said chamber means comprises upper and lower axially spaced annular chambers in fluid communication with said body means through upper and lower port means, respectively, said body means being provided with valve means between said upper and lower port means which when closed pressure isolates said upper chamber from said lower chamber.

11. A pressure operated circulating joint as set forth in claim 10 wherein said upper and lower chambers are partially defined by oppositely facing annular surfaces on said sleeve means.

12. A pressure operated circulating joint as set forth in claim 10 in which said valve means is attached to said body means by connection means adapted to release said valve means from said body means, when said valve means is closed, on the existence of a predetermined pressure differential across said valve means.

13. A pressure operated circulating joint as set forth in claim 7 in which said chamber means comprises first and second axially spaced annular chambers, said first chamber being partially defined by a first annular surface on said sleeve means, said second chamber being partially defined by an oppositely facing second annular surface on said sleeve means so that when equal pressure exist in said first and second chambers, the axial forces on said first and second annular surfaces offset each other.

14. A pressure operated circulating joint as set forth in claim 13 in which said first and second annular chambers communicate with the interior of said body means through axially spaced first and second port means, respectively.

15. A pressure operated circulating joint as set forth in claim 14 in which said body means is provided with valve means, between said first and second port means, closable to isolate said first and second chambers and to create a pressure differential therebetween.

16. A pressure operated circulating joint as set forth in claim 13 in which said chamber means comprises a third chamber axially spaced from said first and second chambers and being partially defined by an annular surface on said blocking means and in fluid communication with the interior of said body means through said circulating port means. 

1. Pressure operated apparatus comprising: a. tubular body means having port means through the walls thereof; b. sleeve means surrounding said body means in a first position blocking fluid flow through said port means, said sleeve means including a skirt member axially movable on the existence of a predetermined pressure level in said body means to unblock flow through said port means; and c. expansible chamber means between said body means and said sleeve means, pressure operable after said unblocking of said port means to axially reposition said sleeve in a second position blocking flow through said port means; d. said skirt member having an annular surface thereon which in said first position forms a portion of a pressure chamber communicating with the interior of said body means through said port means, said skirt member being fastened to the rest of said sleeve means in said first position by connection means, said connection means being releasable on exposure of said annular surface to said predetermined pressure level to permit said axial movement of said skirt means to unblock said port means.
 2. Pressure operated apparatus as set forth in claim 1 in which said expansible chamber means comprises first and second annular chambers communicating with the interior of said body means through first and second ports, respectively.
 3. Pressure operated apparatus as set forth in claim 2 in which said first chamber is partially defined by said annular surface on said skirt member, said second chamber being partially defined by an oppositely facing annular surface on said sleeve means.
 4. Pressure operated apparatus as set forth in claim 3 in which valve means is installed in said body means between said first and second ports, said valve means being closable to pressure isolate one end of said body means interior and said first chamber from the other end of said body means interior and said second chamber.
 5. Pressure operated apparatus as set forth in claim 4, in which said valve means comprises a seat member affixed to said body means in sealing engagement with its interior and a closure member sealingly engageable with said seat member.
 6. Pressure operated apparatus as set forth in claim 5 in which said seat member is affixed to said body means by connection means which is releasable, when said valve means is closed, at a predetermined pressure differential between said first and second chambers.
 7. A pressure operated circulating joint for installation in a pipe string, comprising: a. tubular body means having connection means at each end thereof for connection with adjacent sections of said pipe string; b. circulating port means through the walls of said body means; c. tubular blocking means surrounding said bodY means in a position blocking flow of fluid through said circulating port means and axially movable to a position unblocking flow through said circulating port means; d. sleeve means surrounding said body means and axially movable when said blocking means is in said unblocking position, from a first position to a second position, blocking flow through said circulating port means; e. chamber means between said body means and said blocking means and said sleeve means, exposable to pressure in said body means, to effect said axial movements of said blocking means and said sleeve means; and f. releasable means connecting said blocking means to said sleeve means allowing separation of said blocking means from said sleeve means on the introduction of a predetermined pressure level into said chamber means.
 8. A pressure operated circulating joint as set forth in claim 7 in which said chamber means comprises an annular chamber at least partially defined by the interior of said blocking means and in fluid communication with the interior of said body means through said circulating port means.
 9. A pressure operated circulating joint as set forth in claim 7 in which said sleeve means is connected to said body means by second releasable means allowing said axial movement thereof on the existence of a predetermined pressure differential in said chamber means.
 10. A pressure operated circulating joint as set forth in claim 9 in which said chamber means comprises upper and lower axially spaced annular chambers in fluid communication with said body means through upper and lower port means, respectively, said body means being provided with valve means between said upper and lower port means which when closed pressure isolates said upper chamber from said lower chamber.
 11. A pressure operated circulating joint as set forth in claim 10 wherein said upper and lower chambers are partially defined by oppositely facing annular surfaces on said sleeve means.
 12. A pressure operated circulating joint as set forth in claim 10 in which said valve means is attached to said body means by connection means adapted to release said valve means from said body means, when said valve means is closed, on the existence of a predetermined pressure differential across said valve means.
 13. A pressure operated circulating joint as set forth in claim 7 in which said chamber means comprises first and second axially spaced annular chambers, said first chamber being partially defined by a first annular surface on said sleeve means, said second chamber being partially defined by an oppositely facing second annular surface on said sleeve means so that when equal pressure exist in said first and second chambers, the axial forces on said first and second annular surfaces offset each other.
 14. A pressure operated circulating joint as set forth in claim 13 in which said first and second annular chambers communicate with the interior of said body means through axially spaced first and second port means, respectively.
 15. A pressure operated circulating joint as set forth in claim 14 in which said body means is provided with valve means, between said first and second port means, closable to isolate said first and second chambers and to create a pressure differential therebetween.
 16. A pressure operated circulating joint as set forth in claim 13 in which said chamber means comprises a third chamber axially spaced from said first and second chambers and being partially defined by an annular surface on said blocking means and in fluid communication with the interior of said body means through said circulating port means. 